Field of the Invention
A refrigeration system comprising at least one compressor, which compressor delivers compressed refrigerant gas to at least one condenser, which condenser delivers liquid refrigerant to at least one flow restriction, from which flow restriction low pressure refrigerant flows to at least one evaporator, from which evaporated refrigerant flows back to the compressor, which system comprises at least one sensor for detecting liquid in the suction gas which sensor is connected to a control unit, which control unit performs control of the refrigeration system, which sensor is formed as at least one capacitive sensor, which capacitive sensor comprises at least a first and a second sensor electrode, which capacity censor at least measures the capacity between at least the first and at least the second electrode, at least one of the sensor electrodes are formed as a tube
Description of Related Art
International Patent Application Publication WO 2010/025730 A1 and corresponding U.S. Patent Application Publication 2011/0214438 disclose a method for controlling a flow of refrigerant to an evaporator arranged in a refrigeration system. The refrigeration system further comprises an expansion valve and a compressor, the expansion valve, the evaporator and the compressor being arranged in a refrigerant flow path having refrigerant flowing therein. The method comprises the steps of increasing an opening degree of the expansion valve, thereby increasing a flow of refrigerant to the evaporator sufficiently to substantially eliminate a dry zone of the evaporator, decreasing the opening degree of the expansion valve after a period of time has lapsed, and repeating the steps of increasing and decreasing the opening degree of the expansion valve. Thus, the opening degree of the expansion valve is ‘pulsated’. This causes the superheat value of refrigerant leaving the evaporator to ‘toggle’ between a zero level and a low, but positive, level. Thereby the average superheat value of the refrigerant leaving the evaporator is decreased, and the refrigeration capacity of the evaporator is utilised more efficiently. Simultaneously, it is ensured that the amount of liquid refrigerant being allowed to pass through the evaporator is kept sufficiently low to prevent damage to the compressor.
European Patent Application EP 2 088 405 A2 and corresponding U.S. Pat. No. 8,146,421 concern a method and apparatus for sensing levels of insoluble fluids within a storage vessel utilizing an array of main capacitive sensors having differing geometries. The array of main capacitive sensors gives the ability to measure the levels of insoluble liquids in a vessel. Each of the main capacitive sensors include at least one pair of conductive plates capable of submersion in the at least two insoluble fluids, and the geometries of the pair of conductive plates differ and are distinct, such as in distance or in width, in each of the main capacitive sensors. In addition, the apparatus and method may include at least one reference sensor placed intermittently along the height of the vessel to provide input as to the permittivities of the insoluble fluids.
Japanese Patent Application Publication JP 09 09 6618 A concerns an apparatus with sufficient accuracy for detecting state of a refrigerant, by outputting continuous electric signals proportional to the ratio of gas state and liquid state. Whereby the refrigerant state-detecting apparatus for detecting the state of a refrigerant in a circulation path. A state detection means and a detection circuit are provided in the circulation path. The state detection means has at least two sheets of flat electrodes held via a small gap to the parallel to a flow of the refrigerant, and the detection circuit takes out the change of capacitance of the state detection means in accordance with the change of dielectric constant of the refrigerant liquid as the change of voltage.